Thermoelectric heat pumps are widely used to maintain a constant temperature of operation for optoelectronic devices such as semiconductor lasers. Although these devices are true heat pumps which are capable of applying heat or removing heat they are primarily operated in a cooling mode and accordingly are usually known as thermoelectric coolers (TEC's). The TEC is used in conjunction with a temperature sensor the output of which is stabilized by a control loop which drives the TEC. In such a system a change in TEC current will yield a corresponding change in the sensor output. The ratio of sensor output to TEC input forms a part of the overall control loop gain. For maintaining a given cold-side temperature the sensor/TEC response is inversely dependent on the hot-side temperature of the TEC. Because the control loop must be designed to operate over a wide range of hot-side temperatures, it must also be designed to deal with a large range of gains because of the variation in TEC response. The control loop must be designed to be stable for the maximum expected gain, and this leads to slow response times for conditions under which the TEC response is small so that the overall gain is low.